A large number of endless magnetic tape cartridges and endless tape recording and playback apparatus have been employed in radio broadcasting stations in order to broadcast the radio programs thereof. It is required that these endless tape recording and playback apparatus provide high quality performance with a low percentage of drop-out occurrences due to the particular industrial use required.
It is inherent in the fabrication of endless tapes for use in endless tape cartridges that the ends of the tape be spliced together at at least one point or location by means of splicing tape so that the tape will, in effect, be infinite or endless in length. However, the endless tape tends to cause a drop-out to occur at the location at which the splicing tape is secured to the tape ends in forming the endless tape when the spliced connection of the endless tape passes over the recording or playback head. This problem can be overcome by insuring that the splicing tape is always made to pass over the recording or playback head immediately before the signals are recorded upon the endless tape. This mode of operation, however, of course requires that the detection of the presence of the splicing tape secured upon the endless tape be in fact achieved.
It has previously been proposed to provide a means for optically detecting other tape secured upon a magnetic tape. For example, in such art, the other tape can be detected by means which can sense a change in the intensity of light reflected from the other tape. While this art is therefore advantageous in its detection reliability, it has not been found possible to employ such an optical detection arrangement in conjunction with endless tape recording and playback apparatus and the associated endless tape cartridge case due to a lack of sufficient space for accommodating such a detection arrangement.
It is further known in the detection art, and as disclosed, for example, within U.S. Pat. No. 4,221,316 issued to Jenkins et al., that an alternative detection system or arrangement exists wherein slight movements of the pinch roller, having a permanent magnet associated therewith and disposed near an electrical coil, due to the increased thickness of the endless tape at the splicing junction and as the endless tape and the splicing junction are moved between the pinch roller and the capstan, can be detected as a result of a current being generated within the coil. This type of system is therefore certainly appropriate for detection of the presence of the splicing tape upon the endless tape disposed within the endless tape cartridge case, however, it has also proven somewhat disadvantageous in that the detection performance is sometimes adversely affected by means of small vibrations of the pinch roller during normal tape transport operations.